Bushcricket song as a clue for spermatophore size?
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Bushcricket males of Poecilimon zimmeri transfer large and protein-rich spermatophores during mating, which females directly ingest. There is correlational evidence that heavier males transfer larger nuptial gifts. In no-choice mating trials, females mated randomly with respect to male’s body weight. In contrast, in two-choice mating trials, female bushcrickets exhibit clear choice for the heavier male. This heavier male advantage was also found in pre-mating choice during phonotaxis. With manipulated mute males, females mated at random with regard to body weight of the competitors. The number of physical encounters between a female and males was low in all tests with a single male (no choice) and greater in choice-tests with two competing males. The latencies to mate also differed significantly between treatments. The time mating pairs spent in precopula was short in experiments where the males could hear rivals and significantly longer in all other tests using either a single male or mute males. Thus, acoustic signalling in male bushcrickets seems to signal male body weight. A preference for heavier males may reflect a female’s preference for a larger spermatophore and therefore a greater direct benefit.